Despite petitions calling for his sacking and even fellow unionists accusing him of turning Northern Ireland into a laughing stock, the Democratic Unionist party is sticking by climate change sceptic Sammy Wilson, who is the province's environment minister.

All the major parties in the Northern Ireland assembly have now said Wilson is unfit to hold the office, after he used his powers this week to ban government television adverts from the province's airwaves. Wilson said the Act On CO2 ads were insidious green "propaganda".

In what appeared to be a rebuke from the government in Westminster, Joan Ruddock, the minister for energy and climate change said: "My commitment to this [advertising] campaign is guided by the best science, the most up-to-date information and the evidence – the increasing frequency of extreme weather we are experiencing and seeing across the globe."

However, the only politician with the power to sack the DUP minister is his party colleague, Peter Robinson, Northern Ireland's first minister. Robinson according to senior DUP sources has "absolutely no intention" of firing Wilson, who remains a popular figure inside his party regardless of his unorthodox views on global warming.

The protest against Wilson came from across the board – nationalists, unionists and environmentalists. Roy Beggs junior, the Ulster Unionist spokesman on the environment said:

"Sammy Wilson's views on climate change, whilst mildly amusing, are out of kilter with mainstream political opinion and more importantly the overwhelming consensus view of climate scientists throughout the world. His latest action in trying to block UK government information on energy efficiency again shows his 'himself alone' attitude to environmental matters.

"He has effectively made a Unilateral Declaration of Independence against Her Majesty's Government on this crucial issue and is making Northern Ireland a laughing stock around the world. It is high time the first minister reined this maverick in, or perhaps this is merely a continuation of the DUP's battle against science and reason."

Recently the DUP's education spokesman Mervyn Storey called for creationism to be taught in Northern Ireland's schools alongside Darwin's theory of evolution.

Northern Ireland's Green party set up an online petition yesterday calling for Wilson to be removed. The Greens said the DUP MP for East Antrim had brought "the people and government of Northern Ireland into international disrepute." Friends of the Earth also entered the controversy with its Northern Ireland director John Woods accusing Wilson of being "completely irresponsible" in blocking the Act on CO2 ads.

In the face of growing criticism over the last 24 hours, the Harley-Davidson-riding Wilson remains defiant and has stuck by his assertion that the current rise in global temperatures is not caused by human activity but by natural variation. He regards manmade climate change as a "gigantic con" and an hysterical "semi-religion."

However, a Department of Environment Northern Ireland spokesman stressed yesterday the minister remains committed to saving energy and recycling to save money.

He holds the current environment job as part of the carve-up between the four-party power-sharing coalition that runs Northern Ireland. And while some in the DUP hold more environmentally friendly views he remains one of the party's stalwarts, regarded by first minister Peter Robinson as a vote-winning asset in the unionist heartlands.

Climate scientists and campaigners were divided over how important the incident was. Some fear that such comments from a government minister will be an embarrassment to the UK on the international stage, and encourage climate scepticism, or at least deter people from taking action to reduce their energy use and greenhouse gas emissions.

One leading campaigner likened the latest row to the impact of a programme by Channel 4 in 2007 called The Great Global Warming Swindle, which was widely derided by many scientists, including some who took part, but appeared to have a discernibly negative effect on public opinion about whether humans are to blame for climate change. An Ipsos/Mori poll last summer found six out of 10 people agreed that "many scientific experts still question if humans are contributing to climate change", something experts partly attributed to the TV programme.

Professor Martin Parry, a leading expert on the United Nations Intergovernmental Panel on Climate Change report, said: " I do not mean to be dismissive, but I do not think — outside Northen Ireland — that anyone has heard of him; and I doubt that the IPCC knows of his sceptical views."